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Saw Blades 101: Country Saw Offers Vital Service For Active Blades & Tested Advice
Sawing, Resawing: Steve Mercer of Country Saw & Knife offers tips for sawing logs and resawing cants and lumber with thin-kerf horizontal bandsaws.
By Peter Hildebrandt
Date Posted: 12/1/2007
Salem, Ohio — When you’re dealing with something sharp, it’s a good idea to have some expert advice. Steve Mercer of Country Saw and Knife, Inc. shares his insights and tips for saw blade maintenance and performance with Pallet Enterprise. Many of the tips in this article could help you find the answer to some of your biggest sawing challenges.
Country Saw & Knife services the cutting industry with carbide, metal saws, knives, abrasives, and band saws for nearly any cutting need. Steve Mercer and his father, Richard Mercer, run the company’s band saw divisions and distribute about 300 miles of band saw material each year, helping customers custom fit bandsaw blades to their machines and particular applications.
“I did not come upon this information by chance,” said Steve. “I have acquired it through years of reading and researching authors such as Irwin Post, having discussions with accomplished millers and listening intently to my father, Richard Mercer. I try to use this information practically in my mill in the cutting of logs for my own log home as well as countless feet of board lumber.”
When it comes to cutting wood, working with its problems, pitfalls, and solutions has become the focus of both Steve and Rick’s lives and their business. There is a lot to observe, remember, and do to keep things running well.
In general, more problems arise with the cutting of large diameter logs than smaller ones, and similarly, during the cutting of sloped grains than with straight grains. Other things which can become an issue include high density woods, (more of a problem than for low density) and knots, which are found in all types of wood.
“Keep in mind that some logs have low density wood, but high density or large knots and you always need to prepare for those knots and other challenges,” said Steve.
“In the thin-kerf band industry our bands do not have the rigidity to stay in the cut without applying tension or ‘tightening’ the blade. So, tension is necessary for a straight cut, keeping in mind that more tension does cut straight, but will also put more stress on your blade.”
In addition to being essential for a straight cut, Steve points out that more tension will also place more stress on the blade, the wheel bearings and the wheel surfaces. “Balancing risk with reward is something we all do everyday.
“Another tip is that if you own an actual band tension gauge, I have found that a band-saw that is 1¼” wide, .042 gauge and 7/8” tooth spacing runs best in a range from about 20,000 psi to 35,000 psi. Sharper, less worn and thicker blades run on the lower end, whereas thinner blades or adverse conditions need to be on the higher end of the tension range. I find my own blades run best at usually about 30,000 psi.
Band mills come in all sorts of designs, including horizontal entry, vertical entry and sloped entry. Everything discussed here can be used for any of these types. The only thing needing to be changed, according to Steve, is the point of reference.
Band wheel diameters can influence the gauge or thickness of the blade that best suits each operation. Steve has found that for band wheels less than 19” in diameter, 0.035 gauge blades work best for him. For 19-24” wheels, 0.042 gauge works best. And for diameters from 24” on up, it’s possible to use a thicker blade. On small wheels, you can run thicker blades, but you will pay the price by losing sharpenings due to blade stresses and breaks.
With all else being the same, wider and thicker blades will cut straighter and possibly longer. “But you will pay with the amount of re-sharpening you get, and your wheels may not accommodate a wider blade,” said Steve.
The band wheels themselves come in a variety of types. Flat aluminum or steel wheels will be best suited for blades that have been electrically or flame-tempered on the backer material (harder bodied bandsaw material) to take the metal-on-metal contact without overly stressing. These blades are called hardback. Or these wheels could use a harder backer material such as higher alloy steel, but they will be more expensive. Some examples of these higher alloy steels can be found in M.K. Morse & Lennox bimetal blades, Wood-Mizer’s double hard blades and some European steel. Flat wheels themselves give the added challenge of tracking problems, according to Steve.
“Most steel wheels have a slight hump in them or ‘crown’ which will help you keep the blade tracked to the front of the wheel; keeping the manufacturer’s recommended crown in the wheel is essential. Therefore, re-crowning the wheels periodically is a must. These wheels, as with flat wheels, will be best suited for ‘hard back’ or ‘bimetal’ blades.”
Other wheels have a “V” groove machined into them to accommodate a belt made of rubber mesh, such as a fan belt or one constructed from neoprene. These wheels can be useful as the belt helps the band track to the front of the wheel. “Some Amish-made mills and pallet dismantlers actually run on automotive tires,” said Steve. “The lack of metal on metal contact here, with something like a tire, as well as with “V” belts will enable you to run a true flexible backer band that has only been hardened on the tooth. Thus, it takes the stress of multiple re-sharpenings better.”
The band mills themselves come in a range of horsepower options. The lower horsepower engines will have slower feed rates and may require a less aggressive blade, such as one with less set, gauge, or hook angle on the teeth. With lower horsepowers, it is especially critical to listen to the RPMs of the engine. A loss in RPM means that the blade looses efficiency, so it means the operator will need to slow the feed rate to let the machine catch up — or replace the blade with a sharper one.
Guides on these mills should be set to the manufacturer’s recommendations. The movable guide should be set as close to the log as the log will allow and the backup guide should be set about 1/16” from the back of the blade. Steve uses this guide as a gauge if he notices he’s constantly pushing his blade back against his backup guide. He either needs to slow the feed rate, replace the blade with a sharper one, or increase the tension,” said Steve. “You can run this guide right up against the back of the blade, but you’d better be running a ‘hard back’ or ‘bimetal’ blade to take the metal on metal contact and have a roller type guide rather than a stationary or ‘friction’ guide. But by doing this, you may be disguising the fact that you may be running on low tension. You will heat up and ‘mushroom’ the back edge of your blade, later causing it to stress and break.”
Keeping the blade clean and free of pitch can be achieved by having the correct tooth spacing to clear the sawdust from the cut and with a lubrication system. With a drip type lubrication system, using an organic or synthetic wood lube is beneficial as well as water with dish soap. During the winter months, kerosene, diesel fuel and windshield washer fluid can be effective as well. “I also never put on a new blade without cleaning my wheels of sap and sawdust,” said Steve.
Looking at the Cuts
When looking at the major problems encountered by millers, here is a summary of results occurring in the wood that is cut and the primary cause of such an event.
1) Wavy Cuts: the blade rises and falls in the cut. Possible solutions include:
• Increasing the blade tension
• Decreasing the feed rate
• Sometimes this can happen in the beginning of the cut and then straighten out. If it does, decrease the feed speed when entering the log, let the machine’s RPMs catch up, and then proceed through the cut.
• If it happens in the middle of the cut, you may have hit a knot or high density section, therefore slow the feed rate and/or increase tension. Also check that your movable guide is as close as possible to the log.
2) Washboard Effect: you get regular grooves in the board 1-3 inches apart, caused by vibration in the blade. Possible solutions include:
• Changing the tension by trying to increase at first or decrease if the problem continues.
• Slow the feed rate.
• Change the position of the movable guide, closer first, then back if the problem continues.
• Assure that your blade has the correct tooth spacing for the width of the cut.
• Assure that the “V” belt is tight.
• Assure that all teeth are set properly.
3) Boards are bellied or humped along the width of the board. Possible solutions could be:
• Slow the feed rate.
• Check for off-center pith, or center of the log, which could indicate growth stresses in the wood. If this is the case, try to center the cant around the off-center pith and cut boards as parallel as possible to the tightest growth rings.
• Check that the set is good and blade is sharp on both sides.
Looking at the Blades
It is also possible to tell a lot about the failure of a band saw blade through an inspection of the stresses which show up on the blade itself after use. Some of these blade indicators include:
1) Stress Cracks which the blade may have on the tooth edges. Possible reasons for this might include:
• This is the cutting or working edge. So, if a blade breaks naturally, it should break from the tooth edge, but if it breaks prematurely from these cracks, check that you are using the proper tooth spacing to clear cut.
• Generally: 1-3” cut = 6-3 teeth per inch (tpi)
3-6” cut = 2- ¾ tpi
6-20”cut = ¾ - 7/8 tpi
10-28”cut = 7/8 – 1 tpi
• If you want more re-sharpens from that blade, do not run it as long the next time.
• Generally, if you want to re-sharpen a blade, do not run it till it starts to act dull — that’s too late.
2) Stress Cracks which the blade may have on the back edge. Possible reasons could be:
• Backup guides may be set too close. Be sure the spacing is 1/16” and no more. Also have enough tension on the blade to keep it there or change blades sooner, before dulling occurs.
3) Sap buildup on blade has become too great. Possible reasons could be:
• Your lubricant may not be flowing fast enough.
• Your tooth-spacing may be too small for the cut.
• Wheels were not cleaned before installing a new blade.
4) Inability of blade to fold or unfold after use. Blade may not lay flat, may spring up in ‘potato chip’ shapes or twist. Possible reasons could be:
• The blade was run on a tension setting that was too low.
• Backup guides are too far back, (they should be kept at a 1/16” spacing).
• Feed rate is too high.
5) Mashed or “Mushroomed” back edge of blade. Possible reasons could be:
• Backup guides may be set too close.
• Tension may be too low.
• Feed rate may be too fast.
• Usually this will happen in conjunction with stress cracks on back edge as well as blade twists.
6) Stress Cracks on front and back edge. Possible reasons could be:
• The “V” belt is not tight enough.
• If steel wheels are used in the equipment, be sure they have the proper crown.
• There may be too much play in the wheel bearings.
• You may have a combination of tension and guide problems with your equipment.
“It’s my hope that this information may help you cut wood better and waste less time,” said Steve. “As with any problem, one or more of the above mentioned observations may be coming into play. Try to eliminate them one at a time; control as many variables as possible and experiment.
“I’ve also always thought it an excellent idea to search out companies and mentors who are out there mainly to help you with your problems — not simply justify their cause or sell you a particular product. Play detective and get to the bottom of each problem as quickly as possible. Don’t let them compound. Above all else, observe and learn constantly. Listen to your mill.”